Integrated micro-optical systems

ABSTRACT

An integrated micro-optical system includes at least two wafers with at least two optical elements provided on respective surfaces of the at least two wafers, at least one of the two optical elements being a spherical lens. The resulting optical system presents a high numerical aperture. One of the optical elements may be a refractive element formed in a material having a high index of refraction.

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] The present application claims priority under 35 U.S.C. §120 toco-pending U.S. patent application Ser. No. 09/566,818 filed May 8,2000, which claims priority to U.S. application Ser. No. 09/276,805filed on Mar. 26, 1999, issued as U.S. Pat. No. 6,061,169 on May 9,2000, which claims priority under 35 U.S.C. §119 to U.S. ProvisionalApplication No. 60/079,378 filed on Mar. 26, 1998, the entire contentsof all of which are hereby incorporated by reference in their entiretyfor all purposes.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention is directed to integrating optics on thewafer level, particularly for realizing a high numerical aperturesystem.

[0004] 2. Description of Related Art

[0005] Magneto-optical heads are used to read current high-densitymagneto-optic media. In particular, a magnetic coil is used to apply amagnetic field to the media and light is then also delivered to themedia to write to the media. The light is also used to read from themedia in accordance with the altered characteristics of the media fromthe application of the magnetic field and light.

[0006] An example of such a configuration is shown in FIG. 1. In FIG. 1,an optical fiber 8 delivers light to the head. The head includes aslider block 10 which has an objective lens 12 mounted on a sidethereof. A mirror 9, also mounted on the side of the slider block 10,directs light from the optical fiber 8 onto the objective lens 12. Amagnetic coil 14, aligned with the lens 12, is also mounted on the sideof the slider block 10. The head sits on top of an air bearing sandwich16 which is between the head and the media 18. The slider block 10allows the head to slide across the media 18 and read from or write tothe media 18.

[0007] The height of the slider block 10 is limited, typically tobetween 500-1500 microns, and is desirably as small as possible.Therefore, the number of lenses which could be mounted on the sliderblock is also limited. Additionally, alignment of more than one lens onthe slider block is difficult. Further, due to the small spot required,the optics or overall optical system of the head need to have a highnumerical aperture, preferably greater than 0.6. This is difficult toachieve in a single objective lens due to the large sag associatedtherewith. The overall head is thus difficult to assemble and notreadily suited to mass production.

SUMMARY OF THE INVENTION

[0008] Therefore, it is an object of the present invention to provide anintegrated optical system that substantially overcomes one or more ofthe problems due to the limitations and disadvantages of the relatedart.

[0009] It is another object of the present invention to integratingoptics on the wafer level to create a high numerical aperture system.

[0010] The above and other objects of the present invention may berealized by providing an integrated micro-optical apparatus including adie formed from more than one wafer bonded together, each wafer having atop surface and a bottom surface, bonded wafers being diced to yieldmultiple die, at least two optical elements being formed on respectivesurfaces of each die, at least one of said at least two optical elementsbeing a spherical lens, a resulting optical system of each die having ahigh numerical aperture.

[0011] The die may further include a compensating element whichcompensates for aberrations exhibited by the spherical lens. Thecompensating element may be on a surface immediately adjacent thespherical lens. The compensating element may be a diffractive element oran aspheric lens. The die may include at least one additional refractiveelement, all refractive elements of the die being formed in materialhaving a high numerical aperture. The refractive element may be on abottom wafer and of a material having a higher refractive index thanthat of the bottom wafer. The spherical lens may be made of a materialhaving a higher index of refraction than a wafer on which it is formed,e.g., photoresist.

[0012] The die may include an aperture holding the spherical lens. Thespherical lens in the aperture may be a ball lens. The ball lens mayhave a round spherical surface and a non-spherical surface. Thenon-spherical surface may be flat.

[0013] The bottom surface of the bottom wafer of the more than one waferbonded together may include a layer of material deposited thereon. Thelayer of material may be deposited in accordance with a differencebetween a desired thickness and a measured thickness of the die. Thelayer may have a different refractive index than said bottom wafer. Thespacing between wafers may be varied in accordance with a differencebetween a desired thickness of a wafer and a measured thickness of thewafer. The spacing may be varied in accordance with a difference betweena desired thickness and a measured thickness of the die.

[0014] The above and other objects of the present invention may berealized by providing a method for forming an integrated micro-opticalapparatus including bonding a first wafer and a second wafer together,each wafer having a top surface and a bottom surface; etching aplurality of holes in the first wafer, placing a round spherical lens ineach of the holes of the first wafer, dicing bonded first and secondwafers to yield multiple dies, and, before dicing, forming at least oneoptical element on one of the top surface and the bottom surface of thesecond wafer.

[0015] The method may further include modifying a surface of the roundspherical lens to form a non-spherical surface. The non-sphericalsurface may be flat. The modifying may include polishing. The placingmay include providing bonding material between said round spherical lensand the first wafer. The providing may include coating the roundspherical lens in the hole with a wettable metal and then coating theround spherical lens in the hole with solder. The etching may includeetching the first wafer from both the first and second surface of thefirst wafer.

[0016] Further scope of applicability of the present invention willbecome apparent from the detailed description given hereinafter.However, it should be understood that the detailed description andspecific examples, while indicating preferred embodiments of theinvention, are given by way of illustration only, since various changesand modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will become more fully understood from thedetailed description given herein below and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

[0018]FIG. 1 illustrates a configuration of a high-density flying headmagneto-optical read/write device;

[0019]FIG. 2A illustrates one configuration for the optics to be used informing a slider block;

[0020]FIG. 2B illustrates the spread function of the optical systemshown in FIG. 2A;

[0021]FIG. 3A illustrates a second embodiment of the optics for use insliding block of the present invention;

[0022]FIG. 3B illustrates the spread function of the optical systemshown in FIG. 3A;

[0023]FIG. 4A illustrates a third embodiment of an optical system to beused in the slider block of the present invention;

[0024]FIG. 4B illustrates the spread function of the optical systemshown in FIG. 4A;

[0025]FIG. 5 is a side view of an embodiment of a slider block inaccordance with the present invention;

[0026]FIG. 6 is a side view of another embodiment of a slider block inaccordance with the present invention;

[0027]FIG. 7 is a side view of another embodiment of a slider block inaccordance with the present invention;

[0028]FIG. 8A is a side view of another embodiment of a slider block inaccordance with the present invention;

[0029]FIG. 8B is a bottom view of the embodiment in FIG. 8A;

[0030]FIG. 9 is a cross-section view of an assembly process formanufacturing an integrated micro-optical system of the presentinvention;

[0031]FIG. 10 is a cross-sectional view of an integrated micro-opticalsystem of the present invention made in accordance with the processshown in FIG. 9;

[0032]FIG. 11 is a cross-sectional view of an assembly process formanufacturing an integrated micro-optical system according to anotherembodiment of the present invention;

[0033]FIG. 12 is a cross-sectional view of an integrated micro-opticalsystem of the present invention made in accordance with the processshown in FIG. 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] All of the optical systems shown in FIGS. 2A-4B providesatisfactory results, i.e., a high numerical aperture with good opticalperformance. The key element in these optical systems is thedistribution of the optical power over multiple available surfaces. Thisdistribution may be even over the multiple surfaces. Sufficientdistribution for the high numerical aperture (NA) required is realizedover more than one surface. Due to the high numerical aperture required,this distribution of optical power reduces the aberrations from therefractive surfaces and increases the diffractive efficiency of thediffractive surfaces by reducing the deflection angle required from eachsurface.

[0035] Further, a single refractive surface having a high numericalaperture would be difficult to incorporate on a wafer, since theincreased curvature required for affecting such a refractive surfacewould result in very thin portions of a typical wafer, leading toconcerns about fragility, or would require a thick wafer, which is notdesirable in many applications where size is a major constraint.Further, the precise shape control required in the manufacture of asingle refractive surface having high NA would present a significantchallenge. Finally, the surfaces having the optical power distributedare easier to manufacture, have better reproducibility, and maintain abetter quality wavefront.

[0036] In accordance with the present invention, more than one surfacemay be integrated with an active element such as a magnetic coil bybonding wafers together. Each wafer surface can have optics integratedthereon photolithographically, either directly or through molding orembossing. Each wafer contains an array of the same optical elements.When more than two surfaces are desired, wafers are bonded together.When the wafers are diced into individually apparatuses, the resultingproduct is called a die. The side views of FIGS. 2A, 3A, and 4Aillustrate such dies which consist of two or three chips bonded togetherby a bonding material 25.

[0037] In the example shown in FIG. 2A, a diffractive surface 20 isfollowed by a refractive surface 22, which is followed by a diffractivesurface 24, and then finally a refractive surface 26. In the exampleshown in FIG. 3A, a refractive surface 30 is followed by a diffractivesurface 32, which is followed by a refractive surface 34 which isfinally followed a diffractive surface 36. In the optical system shownin FIG. 4A, a refractive surface 40 is followed by a diffractive surface42 which is followed by a refractive surface 44 which is followed by adiffractive surface 46, which is followed by a refractive surface 48 andfinally a diffractive surface 50. The corresponding performance of eachof these designs is shown in the corresponding intensity spread functionof FIGS. 2B, 3B, and 4B.

[0038] When using spherical refractive elements as shown in FIGS. 2A, 3Aand 4A, it is convenient to follow these spherical refractive elementswith a closely spaced diffractive element to compensate for theattendant spherical aberrations. An aspherical refractive does notexhibit such aberrations, so the alternating arrangement of refractivesand diffractives will not necessarily be the preferred one.

[0039] While the optical elements may be formed using any technique, toachieve the required high numerical aperture, it is preferable that therefractive lenses remain in photoresist, rather than being transferredto the substrate. It is also preferable that the bottom substrate, i.e.,the substrate closest to the media, has a high index of refractionrelative of fused silica, for which n=1.36. Preferably, this index is atleast 0.3 greater than that of the substrate. One example candidatematerial, SF56A, has a refractive index of 1.785. If the bottomsubstrate is in very close proximity to the media, e.g., less than 0.5microns, the use of a high index substrate allows a smaller spot size tobe realized. The numerical aperture N.A. is defined by the following:

N.A.=n sin θ

[0040] where n is the refractive index of the image space and θ is thehalf-angle of the maximum cone of light accepted by the lens. Thus, ifthe bottom substrate is in very close proximity to the media, the higherthe index of refraction of the bottom substrate, the smaller theacceptance half-angle for the same performance. This reduction in angleincreases the efficiency of the system.

[0041] As shown in FIG. 5, the slider block 61 in accordance with thepresent invention includes a die composed of a plurality of chips, eachsurface of which is available for imparting optical structures thereon.The die is formed from wafers having an array of respective opticalelements formed thereon on either one or both surfaces thereof. Theindividual optical elements may be either diffractive, refractive or ahybrid thereof. Bonding material 25 is placed at strategic locations oneither substrate in order to facilitate the attachment thereof. Bysurrounding the optical elements which are to form the final integrateddie, the bonding material or adhesive 25 forms a seal between the wafersat these critical junctions. During dicing, the seal prevents dicingslurry from entering between the elements, which would result incontamination thereof. Since the elements remain bonded together, it isnearly impossible to remove any dicing slurry trapped there between. Thedicing slurry presents even more problems when diffractive elements arebeing bonded, since the structures of diffractive elements tend to trapthe slurry.

[0042] Advantageously, the wafers being bonded include fiducial markssomewhere thereon, most likely at an outer edge thereof, to ensurealignment of the wafers so that all the individual elements thereon arealigned simultaneously. Alternatively, the fiducial marks may be used tofacilitate the alignment and creation of mechanical alignment featureson the wafers. One or both of the fiducial marks and the alignmentfeatures may be used to align the wafers. The fiducial marks and/oralignment features are also useful in registering and placing the activeelements and any attendant structure, e.g., a metallic coil and contactpads therefor, on a bottom surface. These active elements could beintegrated either before or after dicing the wafers.

[0043] On a bottom surface 67 of the slider block 61 in accordance withthe present invention, a magnetic head 63 including thin film conductorsand/or a magnetic coil is integrated using thin film techniques, asdisclosed, for example, in U.S. Pat. No. 5,314,596 to Shukovsky et al.entitled “A Process for Fabricating Magnetic Film Recording Head for usewith a Magnetic Recording Media.” The required contact pads for themagnetic coil are also preferably provided on this bottom surface.

[0044] Since the magnetic coil 63 is integrated on the bottom surface67, and the light beam is to pass through the center of the magneticcoil, it is typically not practical to also provide optical structureson this bottom surface. This leaves the remaining five surfaces 50-58available for modification in designing an optical system. Further,additional wafers also may be provided thereby providing a total ofseven surfaces. With the examples shown in FIGS. 2A and 3A the surface50 would correspond to surface 20 or 40, respectively, the surface 52would correspond to surface 22 or 32, respectively, the surface 54 wouldcorrespond to surface 24 or 34, respectively, and the surface 56 wouldcorrespond to surface 26 or 36, respectively.

[0045] Each of these wafer levels can be made very thin, for example, onthe order of 125 microns, so up to four wafers could be used even underthe most constrained conditions. If size and heat limitations permit, alight source could be integrated on the top of the slider block, ratherthan using the fiber for delivery of light thereto. In addition to beingthin, the use of the wafer scale assembly allows accurate alignment ofnumerous objects, thereby increasing the number of surfaces containingoptical power, which can be used. This wafer scale assembly also allowsuse of passive alignment techniques. The other dimensions of the sliderblock 61 are determined by the size of the pads for the magnetic coil,which is typically 1500 microns, on the surface 67, which is going to bemuch larger than any of the optics on the remaining surfaces, and anysize needed for stability of the slider block 61. The bottom surface 67may also include etch features thereon which facilitate the sliding ofthe slider block 61.

[0046] Many configurations of optical surfaces may be incorporated intothe slider block 61. The bonding, processing, and passive alignment ofwafers is disclosed in co-pending, commonly assigned U.S. applicationSer. No. 08/727,837 entitled “An Integrated Optical Head for Disk Drivesand Method of Forming Same” and U.S. Pat. No. 6,096,155 entitled “AWafer Level Integration of Multiple Optical Heads” which are both herebyincorporated by reference in their entirety.

[0047] Additionally, an optical element can be provided on the bottomsurface 67 of the bottom wafer as shown in FIG. 6. When providing anoptical element on this bottom surface 67, a transparent layer 65,having a different refractive index than that of the wafer itself isprovided between the bottom surface 67 and the coil 63. The differencein refractive index between the layer 65 and the wafer should be atleast approximately 0.3 in order to insure that the optical effect ofthe optical element provided on the bottom surface 67 is discernable.Also as shown in FIG. 6, a single wafer may be used if sufficientperformance can be obtained from one or two optical elements.

[0048] Further as shown in FIG. 6, metal portions 69 may be provided toserve as an aperture for the system. These apertures may be integratedon any of the wafer surfaces. The aperture may also serve as theaperture stop, typically somewhere in the optical system prior to thebottom surface thereof. When such metal portions 69 serving as anaperture are provided on the bottom surface 67, it is advantageous toinsure the metal portions 69 do not interfere with the operation of themetal coil 63.

[0049] A problem that arises when using a system with a high numericalaperture for a very precise application is that the depth of focus ofthe system is very small. Therefore, the distance from the opticalsystem to the media must be very precisely controlled to insure that thebeam is focused at the appropriate position of the media. For the highnumerical apertures noted above, the depth of focus is approximately 1micron or less. The thicknesses of the wafers can be controlled towithin approximately 1-5 microns, depending on the thickness anddiameter of the wafer. The thinner and smaller the wafer, the better thecontrol. When multiple wafers are used, the system is less sensitive toa variation from a design thickness for a particular wafer, since thepower is distributed through all the elements.

[0050] When using multiple wafers, the actual thickness of each wafercan be measured and the spacing between the wafers can be adjusted toaccount for any deviation. The position of the fiber or source locationcan be adjusted to correct for thickness variations within the waferassembly. Alternatively, the design of a diffractive element may bealtered in accordance with a measured thickness of the slider block inorder to compensate for a variation from the desired thickness.Alternatively, the entire system may be designed to focus the light at aposition deeper than the desired position assuming the thicknesses areprecisely realized. Then, the layer 65 may be deposited to provide theremaining required thickness to deliver the spot at the desiredposition. The deposition of the layer 65 may be more preciselycontrolled than the formation of the wafers, and may be varied toaccount for any thickness variation within the system itself, i.e., thelayer 65 does not have to be of uniform thickness. If no optical elementis provided on the bottom surface 67, then the refractive index of thelayer 65 does not need to be different from that of the wafer.

[0051]FIG. 7 is a side view of another embodiment of the slider block.As shown in FIG. 7, the fiber 8 is inserted into the top wafer and themirror 9 is integrated into the top wafer, preferably at a 45-degreeangle. Light reflected by the mirror 9 is directed to a diffractiveelement 71, followed by a refractive element 73, followed by adiffractive element 75, followed by a refractive element 77, anddelivered through the coil 63. For such a configuration, the top surface50 is no longer available for providing an optical element.

[0052] Additionally, for fine scanning control of the light, the mirror9 may be replaced with a micro-electro-mechanical system (MEMS) mirrormounted on a substrate on top of the top chip. A tilt angle of the MEMSis controlled by application of a voltage on a surface on which thereflector is mounted, and is varied in accordance with the desiredscanning. The default position will preferably be 45 degrees so theconfiguration will be the same as providing the mirror 9.

[0053] An additional feature for monitoring the spot of light outputfrom the slider block is shown in FIGS. 8A and 8B. As shown in FIG. 8A,in addition to the optical system, consisting of, for example,diffractive elements 87, 89, used for delivering light through themagnetic coil 63, monitoring optical elements 81, 83 are provided. Themonitoring optical elements 81, 83 are of the same design as theelements of the optical system 87, 89, respectively. In other words, themonitoring optical elements are designed to focus at a same distance asthat of the optical system. Advantageously, the monitoring opticalelements 81, 83 are larger than the optical system elements for ease ofconstruction and alignment of the test beam. In the configuration shownin FIGS. 8A and 8B, the monitoring optical elements 81, 83 areapproximately twice the size of the element 87, 89. The monitoringsystem also includes an aperture 85, preferably formed by metal. It isnoted that FIG. 8B does not show the magnetic coil 63.

[0054] During testing, light is directed to the monitoring opticalsystem to insure that light is being delivered to the aperture at thedesired location. The magnitude of light passing through the aperturewill indicate if the optical system is sufficiently accurate, i.e., thatthe light is sufficiently focused at the aperture to allow apredetermined amount of light through. If the light is not sufficientlyfocused, the aperture will block too much of the light.

[0055] Thus, by using the monitoring system shown in FIGS. 8A and 8B,the optical system of the slider block may be tested prior to itsinsertion into the remaining device, even after being integrated withthe active element 63. The dimension requirement imposed by the contactpads for the magnetic coil 63 and the coil itself result in sufficientroom available on the wafers for the inclusion of such a monitoringsystem, so the size of the slider block is unaffected by theincorporation of the monitoring system.

[0056]FIGS. 9 and 11 illustrate basic process steps for forming anintegrated microoptical system, with FIGS. 10 and 12 illustrating thesystem formed thereby, respectively.

[0057] In FIG. 9, only the basic fabrication process is illustrated,with anti-reflective coatings, intermediate lithography steps andadhesive deposition being omitted for clarity. Multi-layer lithographyand etching is used to fabricate a shallow aspheric element 102 in asubstrate 104, e.g., synthetic fused silica. Then, front-back alignmentis used to provided photoresist on the substrate 104 opposite theshallow aspheric element 102. This photoresist is reflowed to form arefractive lens 106. On another substrate 108, illustratively a highindex substrate glass that has been polished to a precise thicknesstolerance, photoresist is provided and reflowed to form anotherrefractive lens 110.

[0058] The substrates 104, 108 are then bonded together using a bondingmaterial 112, illustratively an ultraviolet curable adhesive. As shownin FIG. 9, the refractive lens 110 is adjacent the shallow asphericelement 102. A resultant optical element 120 is preferably made on awafer level, and the resultant optical element 120 is realized by dicingthe wafer containing multiple resultant optical elements 120 alongdicing lines 114. The shallow aspheric element 102 is optional and isprovided to correct for aberrations introduced by the photoresist lens106, 110. FIG. 10 schematically illustrates the functioning of theresultant optical element 120 formed by the process shown in FIG. 9.

[0059] A fabrication process used when including a high index ball lensis shown in FIG. 11. A wafer 130, e.g., a silicon wafer, is patternedand etched to from holes 132 therein. This hole 132 is to receive a highindex ball lens 134. Illustratively, the ball lens 134 is secured in thehole 132 by applying a thin layer of wettable metal 136 over the entiresurface. Then, solder 138 is plated over the surface. The wettable metal136 provides surface tension which will pull the solder 138 into abinding region around the ball lens 134, securing the ball lens 134 inthe hole 132. The wafer 130 is then polished to flatten a surface 135 ofthe ball lens 134. The use of a ball lens, while not allowing formationthereof on a wafer level, is advantageous in precise knowledge of theexact profile thereof and allows for a deeper sag to be realized.

[0060] Similarly as shown in FIG. 9, on another substrate 140, amulti-layer lithography and etching is used to fabricate a shallowaspheric element 142 in the substrate 140, e.g., synthetic fused silica.Then, front-back alignment is used to provided photoresist on thesubstrate 140 opposite the shallow aspheric element 142. Thisphotoresist is reflowed to form a refractive lens 144.

[0061] The substrates 130, 140 are then bonded together using a bondingmaterial 146, illustratively an ultraviolet curable adhesive. As shownin FIG. 1, the curved surface of the ball lens 134 is adjacent theshallow aspheric element 142. A resultant optical element 150 ispreferably made on a wafer level, and the resultant optical element 150is realized by dicing the wafer containing multiple resultant opticalelements 150 along dicing lines 148. The shallow aspheric element 142 isoptional and is provided to correct for aberrations introduced by thelenses 134, 144. FIG. 12 schematically illustrates the functioning ofthe resultant optical element 150 formed by the process shown in FIG.11.

[0062] The invention being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed:
 1. An integrated micro-optical apparatus comprising adie formed from more than one wafer bonded together, each wafer having atop surface and a bottom surface, bonded wafers being diced to yieldmultiple die, at least two optical elements being formed on respectivesurfaces of each die, at least one of said at least two optical elementsbeing a spherical lens, a resulting optical system of each die having ahigh numerical aperture.
 2. The integrated micro-optical apparatus ofclaim 1, wherein the die further comprises a compensating element whichcompensates for aberrations exhibited by the spherical lens.
 3. Theintegrated micro-optical apparatus of claim 2, wherein the compensatingelement is on a surface immediately adjacent the spherical lens.
 4. Theintegrated micro-optical apparatus of claim 3, wherein the compensatingelement is a diffractive element.
 5. The integrated micro-opticalapparatus of claim 3, wherein the compensating element is an asphericlens.
 6. The integrated micro-optical apparatus of claim 1, wherein thedie includes at least one additional refractive element, all refractiveelements of the die being formed in material having a high numericalaperture.
 7. The integrated micro-optical apparatus of claim 6, whereinthe refractive element is on a bottom wafer and is of a material havinga higher refractive index than that of the bottom wafer.
 8. Theintegrated micro-optical apparatus of claim 1, wherein said die furthercomprises an aperture holding said spherical lens.
 9. The integratedmicro-optical apparatus of claim 8, wherein spherical lens in saidaperture is a ball lens.
 10. The integrated micro-optical apparatus ofclaim 9, wherein said ball lens has a round spherical surface and anon-spherical surface.
 11. The integrated micro-optical apparatus ofclaim 10, wherein said non-spherical surface is flat.
 12. The integratedmicro-optical apparatus of claim 1, wherein a bottom surface of a bottomwafer of said more than one wafer bonded together includes a layer ofmaterial deposited thereon.
 13. The integrated micro-optical apparatusof claim 12, said layer of material is deposited in accordance with adifference between a desired thickness and a measured thickness of thedie.
 14. The integrated micro-optical apparatus of claim 1, wherein saidlayer has a different refractive index than said bottom wafer.
 15. Theintegrated micro-optical apparatus of claim 1, further comprising aspacer between wafers, a thickness of the spacer being determined inaccordance with a difference between a desired thickness of a wafer anda measured thickness of the wafer.
 16. The integrated micro-opticalapparatus of claim 15, wherein said spacing is varied in accordance witha difference between a desired thickness and a measured thickness of thedie.
 17. The integrated micro-optical apparatus of claim 1, wherein saidspherical lens is made of a material having a higher index of refractionthan a wafer on which it is formed.
 18. The integrated micro-opticalapparatus of claim 17, wherein said material of the spherical lens isphotoresist.
 19. A method for forming an integrated micro-opticalapparatus comprising: bonding a first wafer and a second wafer together,each wafer having a top surface and a bottom surface; etching aplurality of holes in said first wafer; placing a round spherical lensin each of said holes of said first wafer; dicing bonded first andsecond wafers to yield multiple dies; and before said dicing, forming atleast one optical element on one of the top surface and the bottomsurface of said second wafer.
 20. The method of claim 19, furthercomprising modifying a surface of said round spherical lens to form anon-spherical surface.
 21. The method of claim 20, wherein thenon-spherical surface is flat.
 22. The method of claim 20, wherein saidmodifying includes polishing.
 23. The method of claim 19, wherein saidplacing includes providing bonding material between said round sphericallens and said first wafer.
 24. The method of claim 23, wherein saidproviding includes coating the round spherical lens in the hole with awettable metal and then coating the round spherical lens in the holewith solder.
 25. The method of claim 19, wherein said etching includesetching said first wafer from both the first and second surface of saidfirst wafer.